Variable rate spring



Sept 21, 1965 HREBICEK 3,207,496

VARIABLE RATE SPRING Filed Nov. 18, 1963 INVENTOR. JAMES HREBICEK 3,207,496 VARIABLE RATE SPRING James Hrebicek, 2327 61st Ave., Cicero, Ill. Filed Nov. 18, 1963, Ser. No. 324,468 7 Claims. c1. 267-1) This invention relates to variable rate spring mechanisms. For purposes of illustration it will be described with reference to its application to a recoil mechanism for a gun, but his understood that in certain of its forms, it may be used generally where a variable rate spring effect is desired.

In my co-pending application, Serial No. 267,535, filed March 25, 1963, for Spring Recoil Mechanism for Gunstock, there is disclosed and claimed a recoil mechanism com rising relatively movable cam surfaces, guide means for controlling the movement of the cam surfaces toward United States Patent one another, a follower mechanism comprising two pivoted parts, each part adapted to cooperate with one of said cams, an abutment member on one of the relatively movable parts, and a spring adapted to be compressed between the abutment and the pivot for the two-part follower. In such arrangement relative movement of the two cams toward one another results in an oscillation of the axis of the spring about the abutment therefor, and, due to the fixed nature of the abutment, the spring as sumes an ar cuate'form which is unsatisfactory.

An object of this invention is the provision of means for maintaining the spring of a resilient system of the type described in my aforesaid application for patent in a straight condition, so that as said spring moves in response to movement of the two-part follower, its axis is always parallel to its original relaxed position.

In the adaptation to a gunstock disclosed in my aforesaid application, it was found that certain marksmen adopt a support for the gun, when it is aimed at a target, which is such that the recoil mechanism is actuated to a considerable extent before the gun is fired. Thus, 2. marksman maybe accustomed to hold the gunstock against his shoulder with considerable force to attain maximum rigidity of support and consequently maximum accuracy. If a gunstock is used which is yieldable when so held be cause of the resilience of the recoil mechanism used therein, the marksman may refuse to use such gunstock even though the recoil mechanism therein would relieve him of considerable pain. 7

Another object of this invention is the provision of means for interposing a slight initial resistance to the operation of the recoil mechanism so that when the mechanism is used in a gunstock and the gun is held in a manner to exert pressure upon the gunstock to achieve rigidity of support, such pressure will be resisted, thereby giving the marksman the feeling of a solid gunstock.

These and other objects of this invention will become apparent from the following detailed description of a preferred. embodiment of this invention when taken together with the accompanying drawings wherein:

FIG. 1 is a side elevational view of a gun to which the recoil mechanism of this invention has been applied in the gunstock thereof;

FIG. 2 is a section on an enlarged scale through the gunstock of the gun of FIG. 1 taken along the line 22 of FIG. 3 showing the improved spring mechanism as applied thereto;

FIG. 3 is a section'through the gunstock of FIG. 2 taken along line 33 thereof and in the direction of the arrows at the ends of said line; and

FIG. 4 is an enlarged sectional view of a portion of FIG. 2.

Referring first to FIG. 1, which shows a typical rifle used by marksmen, the mechanism of this invention is Patented Sept. 21, 1965 shown installed in the gunstock thereof, said gunstock being comprised of two parts 10 and 11, which are relatively movable in a longitudinal direction in a manner controlled by the recoil mechanism of this invention. It is intended that when the gun is held against a rifiemans shoulder and fired the recoil mechanism will absorb a major part of the recoil and hence will lessen the discomfort in general attendant upon firing many rounds of high-powered shells.

The recoil mechanism is shown more clearly in FIGS. 2 and 3. Each of said parts, 10 and 11, is hollow to receive action and reaction elements 12 and 13 respectively. These elements may be interchanged insofar as parts 10 and 11 are concerned; that is to say, element 12 may become the reaction element and element 13 the action element. Each element is rigid, element 12 comprising a thick plate preferably made as a casting which fits within the bottom of the hollow portion '14 in part 10. As an integral part of element 12 there may be formed, in the casting process, a cam 15 having a cam surface 16 thereon. Element 13 is comprised of a pair of spaced plates 17 and 18'connected by struts 19 and 20. Said plates 17, 18 and struts 19 and 20 may similarly be formed as an integral casting, and plate 17 may have formed thereon a cam 21 having a cam surface 22 thereon. The reaction element 13 is secured by screws 23, or the like, to gunstock part 11, and action element 12 is secured by screws 24 to gunstock part 10.

Movement of part 11 relative to part 10 is controlled by a pair of spaced shoulder screws 25 and 26, which are secured at their threaded ends to action element 12 and at their head ends pass through close-fitting openings 27 in plate 17 formed in a boss 28 thereon. Heads 29 of screws 25 and 26 limit the separation of the action and reaction elements. Thus, screws 25 and 26 serve as guides for the movement of reaction element 13 relative to action element 12 and also serve as supports for the entire gunstock part 11.

Cooperating with cam surfaces 16 and 22 is a follower 30 which is comprised of two parts 31 and 32, each part being substantially triangular in form and each having spaced rollers 33, 34, and 35, 36 contacting cam surfaces 16 and 22, respectively. Said parts 31 and 32 are connected together by a pivot 37, so that each part may follow its cam surface and change its angularity relative to the other part, as required by the form and disposition of said cam surfaces 16 and 22.

Also pivoted on pivot 37 is a spring holder 38, the construction being such that spring holder 38 has a single tongue 39 through which pivot 37 passes, and parts 31' and 32 have bifurcated ends 40 and 41 (FIG. 3), all in nested relation to one another so that cams 15' and 21 and their followers 31 and 32 may have a co-planar relationship. Thus, tongue 39 is received in the bifurcated end 40 of part 31 and the bifurcated end 40 of part 31 is received in the bifurcated end 41 of part 32. Spaced from spring holder 38 is a bar 42 in which is a threaded opening 43 to receive an externally threaded tube 44. Spring holder 38 has a pin 45 which extends into tube 44 with a sliding fit to guide the'spring holder and to maintain it in fixed relation to bar 42.

A flanged nut 46 is threaded on tube 44, and a spring 47 is retained between nut 46 and spring retainer 38. It is contemplated that spring 47 will be in compression between nut 46 and'retainer 38, and to this end the reaction of said spring is taken by two pairs of levers 48, 48a and 49'shown pivotally secured at their ends to cams 15, 21 and bar 42. It is understood that said levers may be pivotally secured to any element of which said cams are a part or to which said cams are secured. The pivots at bar 42 are shown at 50 and 51, and the pivots at the cams are shown at 52 and 53. Several openings, such as 54, 55, 56 and 57, may be provided for pivots 52, 53 to change the angularity of the levers with respect to bar 42 and thus to change the spring rate. The initial compression of spring 47 may be varied by varying the position of nut 46 relative to spring holder 38. This can be accomplished either by turning nut 46 on tube 44, or by turning the tube and nut relative to bar 42.

It may be apparent from the description thus far given that as cams 15 and 21 move toward and away from one another, followers 31, 32 roll on cam surfaces 16 and 22 and pivot 37 will move transversely of gunstock 11 toward and away from bar 42. The movement of bar 42 is controlled by levers 48 and 49, and since these levers are of identical size, and are symmetrically pivoted with respect to follower 30, pivot 37 will aways be on the perpendicular bisector of a line connecting pivots 50 and 51. Thus spring 47 will always be compressed along its axis and will generate no undesirable side forces. This action will obtain regardless of which symmetrical pairs of openings 5457 are used and whatever the distance between pivots 50 and 51.

The initial deflection of spring 47 requires the least force, and hence spring 47 is readily deflected by a rifleman who, to achieve greatest accuracy, uses a shoulder strap while in a prone position to hold the butt of the rifle firmly against his shoulder. This deflection may cause him to lose the feeling of firmness he seeks by the use of the strap and hence may cause him to forego the advanv tages of the above-described recoil mechanism. The firmness sought by the rifleman is provided by a device which is pressure responsive so that it will not yield under the pressures exerted by the rifleman, but will yield under the recoil of a discharged shell.

The restraining device in its preferred form comprises a ball detent 58 disposed in an opening 59 in a boss 60 in plate 17. Said opening 59 is threaded and is closed by an adjusting screw 61. A spring 62 is compressed between screw 61 and ball detent 58 and serves to hold said ball detent 58 and serves to hold said ball resiliently in a groove 63 in shoulder screw 26. Said ball detent serves to hold screw 26 against axial movement until a force is impressed axially upon said screw which is suflicient to cam said ball out of groove 63. The magnitude of the axial force required is a function of the pressure of spring 62 upon ball 58. Since there are two shoulder screws 25 and 26, two restraining devices can be used, and if these are not suflicient, two or more restraining devices can be used with each screw, arranged either axially along said screw or circumferentially therearound. Other forms and locations of force responsive release devices will suggest themselves to those skilled in the art.

It may be appreciated that some of the recoil of a discharged shell is absorbed in releasing or overcoming the resistance of ball detent 58 and hence the rate of the spring 47 and the curvature of the cam surfaces 16 and 22 may be determined to take advantage of the work done by ball detent 58. Thus spring 47 may be initially Weaker than it would be without ball detent 58.

The recoil mechanism described above can be used with other firearms, and in fact, can be used in industry and on conveyances generally where an adjustable, variable rate shock absorbing device is required. Said recoil mechanism can be used with or without the above force responsive restraining device, depending upon the use to which the recoil mechanism is to be put. Thus the recoil mechanism can be used under punch presses, drop forges, or like industrial machinery, and can be used as a spring suspension for wheeled vehicles. It is understood therefore that the foregoing description is merely illustrative of a preferred embodiment of the invention and that the scope of the invention is not to be limited thereto, but is to be determined by the appended claims.

I claim:

1. A variable rate spring mechanism comprising relatively reciprocable action and reaction elements, cam surfaces on said elements, said surfaces diverging with respect to one another, a follower for each cam surface, means pivotally connecting said followers together, individual levers pivoted at one end to each element and pivoted at their opposite end to a common member, and resilient means having one end connected to the common member and its other end connected to the means pivotally connecting said followers, said common member being moved in unison with the pivot by said levers and thereby causing both ends of the spring to move in unison as the action and reaction elements reciprocate relative to one another.

2. A variable rate spring mechanism as described in claim 1, and means for changing the rate of said resilient means.

3. A variable rate spring mechanism as described in claim 1, said common member comprising a bar, and spring-retaining means on said bar cooperating with said one end of said resilient means.

4. A variable rate spring mechanism as described in claim 1, said common member comprising a bar having a threaded opening therein, a threaded tube in said opening, a flanged spring-retaining nut on said tube; said means pivotally connecting said followers together having a pin slidably received in said tube and guided thereby, and said resilient means comprising a helical spring encircling said tube and pin.

5. A variable rate spring mechanism as described in claim 1, and force responsive detent means cooperating with said elements and preventing relative movement between said elements until .a predetermined force is impressed upon one of said elements in the direction of the other of said elements.

6. A variable rate spring mechanism as described in claim 1, guide means cooperating with said action and reaction elements to control relative movement therebetween, and force-responsive detent means cooperating with said guide means and with one of said elements and preventing movement between said elements until a predetermined force is impressed upon one of said elements in the direction of the other of said elements.

7. A variable rate spring mechanism as described in claim 1, said reaction element having an opening therein, a shoulder screw slidably received in said opening and threaded into the action member to guide the movement of the action member relative to said reaction member, said shoulder screw having a peripheral groove adapted in the inactive state of the action member to be received in the opening in the reaction member, a transverse opening in the reaction member aligned with said groove in the inactive state of the action member, a ball disposed in said transverse opening and adopted to be received in said groove, resilient means in said transverse opening and bearing against said ball to retain said ball in said groove, and screw means in said transverse opening acting upon said resilient means in said transverse opening to compress the latter resilient means against said ball.

References Cited by the Examiner UNITED STATES PATENTS 426,916 4/90 Cash et al 4274 X 480,587 8/92 Jones et a1. 4274 3,001,312 9/61 Campbell 4274 FOREIGN PATENTS 6,030 1908 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner. 

1. A VARIABLE RATE SPRING MECHANISM COMPRISING RELATIVELY RECIPROCABLE ACTION AND RECTION ELEMENTS, CAM SURFACES ON SAID ELEMENTS, SAID SURFACES DIVERGING WITH RESPECT TO ONE ANOTHER, A FOLLOWER FOR EACH CAM SURFACE, MEANS PIVOTALLY CONNECTING SAID FOLLOWERS TOGETHER, INDIVIDUAL LEVERS PIVOTED AT ONE END TO EACH ELEMENT AND PIVOTED AT THEIR OPPOSITE END TO A COMMON MEMBER, AND RESILIENT MEANS HAVING ONE END CONNECTED TO THE COMMON MEMBER AND ITS OTHER END CONNECTED TO THE MEANS PIVOTALLY CONNECTING SAID FOLLOWERS, SAID COMMON MEMBER BEING MOVED IN UNISON WITH THE PIVOT BY SAID LEVERS AND THEREBY CAUSING BOTH ENDS OF THE SPRING TO MOVE IN UNISON AS THE ACTION AND REACTION ELEMENTS RECIPROCATE RELATIVE TO ONE ANOTHER. 